Temporary pacing of the heart, for instance after open-heart surgery, has been found to be effective in the treatment of postoperative cardiac arrhythmias which arise, for example, as a result of damage or injury to the conduction system during the surgery, hypothermia, preoperative anti-arrhythmia therapy (beta-blockers, calcium antagonists, digoxin) local edema, or temporary and intraoperative ischemia. In these cases, the heart's performance can show marked improvement when a relatively slow heart rate is elevated by electronic pacing. Patients who show postoperative sinus bradycardia can achieve improvements through AV sequential pacing.
For temporary pacing, one or more electrodes at the distal end of a lead are affixed to the heart, for instance to the epicardium or myocardium. Another electrode is attached to the outer skin surface or to the epicard or myocard as well. The distal end of the lead remains outside the body where electrical and mechanical connections to an external temporary pacemaker together with the skin electrode are made.
In the description herein, an element or end which is referred to as “proximal” is closer to a first tissue (e.g. closer to the heart or cardiac tissue) wherein an element or end which is referred to as “distal” is farther from a first tissue (e.g. farther from the heart or cardiac tissue).
A variety of methods have been used for embedding an electrode in the heart. One method utilizes a “zigzag” or helical shaped electrode. Prior to deployment, the zigzag or helical shaped electrode is rather compressed, but becomes spread out when pulled though the myocardium. Pacing electrodes of this kind are disclosed, for example, in U.S. Pat. No. 5,350,419 to Bendel et al. and U.S. Pat. No. 4,341,226 to Peters et al.
When pacing is no longer needed, or before the patient is discharged from the ward, the lead is detached from the heart by gently tugging on the external portion of the lead. The lead is then pulled out of the thorax and disposed of. Thus, on the one hand, the fixation of the lead to the heart must be stable enough to guarantee reliable heart pacing during the entire pacing period, and on the other hand, the fixation must not be too securely anchored in the heart so that it can be removed without injury upon tugging. Nonetheless, removal of an implanted lead entails a risk of damaging and/or rupturing the myocardium and/or a different part of the heart when the lead is pulled out. This can cause severe bleeding and/or cardiac tamponade, which can be a life threatening condition.